Patchy dense fog has formed in a few areas this morning (see visibility map below) and where this occurs the very cold temperatures – near or well below zero allow moisture to condense on cold surfaces, creating slick spots on highways and localized icy conditions on streets, sidewalks, driveways and parking lots. Where this glaze forms, conditions will become extremely slick and dangerous, so take precautions, if outside this morning.

Tonight snow-covered highways and slick/icy conditions will again develop, as another upper-air low pressure disturbance swings over our area from the west, bringing another round of steady accumulating snow, perhaps on the order of 2 to 3-inches.

The snow will probably begin in westernmost sections along Interstate-39 and the Fox River Valley toward evening and spread east across Chicago into northwest Indiana by 9PM or so – continuing overnight. Snow will end from the west Wednesday morning, but anticipate another slow commute and slick/icy conditions.